1. Technical Field
The present invention relates to a choke coil, and more particularly, to a choke coil that may be used as a common mode filter, or the like, of an electromagnetic interference (EMI) filter.
2. Description of the Related Art
Recently, efforts to increase a processing speed of products, while reducing an overall size and thickness of the exterior thereof, have continued in the market in flat panel displays (FPDs) such as liquid crystal displays (LCDs), plasma display panels (PDPs), and light emitting diodes (LEDs), or the like, which, however, accompanies various problems arising due to electromagnetic interference (EMI).
Meanwhile, a power supply device is essential for display devices or any other electric/electronic devices to supply power, and among power supply devices, a switching mode power supply (SMPS) using a switching function of a semiconductor device and a power conversion function of a transformer converts commercial power into highly efficient and high quality power required for various electronic products and supplies the same.
However, the SMPS causes a large amount of noise due to electromagnetic interference (EMI) when a switching operation is performed.
EMI may be divided into conducted emission EMI and radiated emission EMI, and the conducted emission EMI and the radiated emission EMI may also be classified into a differential mode noise and a common mode node, respectively.
In order to cancel such EMI as mentioned above, an EMI filter may be employed in a power source input terminal to which commercial alternating current (AC) power is input, as disclosed in Prior Art Document.
In detail, in order to reduce differential mode noise, the EMI filter mainly uses a normal mode choke coil and an X capacitor, and in order to reduce common mode noise, the EMI filter uses a common mode choke coil and a Y capacitor.
The EMI filter employs a choke coil having a low frequency band and a choke coil having a high frequency band to secure a large frequency band to cancel electromagnetic interference, which, however, results in an increase in an overall size of the exterior of a product, failing to meet the consumer demand for lighter, thinner, shorter, and smaller products.
Meanwhile, in an EMI filter, magnetizing inductance Lm characteristics of a choke coil may reduce common mode noise and leakage inductance Lk characteristics thereof may reduce differential mode noise, but in a situation in which products are increasingly reduced in size and thickness, there is a limitation in increasing both magnetizing inductance Lm and leakage inductance Lk.